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diff --git a/man/nss-systemd.xml b/man/nss-systemd.xml new file mode 100644 index 0000000..b7b4538 --- /dev/null +++ b/man/nss-systemd.xml @@ -0,0 +1,183 @@ +<?xml version='1.0'?> <!--*-nxml-*--> +<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN" + "http://www.oasis-open.org/docbook/xml/4.2/docbookx.dtd"> +<!-- SPDX-License-Identifier: LGPL-2.1-or-later --> + +<refentry id="nss-systemd" conditional='ENABLE_NSS_SYSTEMD'> + + <refentryinfo> + <title>nss-systemd</title> + <productname>systemd</productname> + </refentryinfo> + + <refmeta> + <refentrytitle>nss-systemd</refentrytitle> + <manvolnum>8</manvolnum> + </refmeta> + + <refnamediv> + <refname>nss-systemd</refname> + <refname>libnss_systemd.so.2</refname> + <refpurpose>UNIX user and group name resolution for user/group lookup via Varlink</refpurpose> + </refnamediv> + + <refsynopsisdiv> + <para><filename>libnss_systemd.so.2</filename></para> + </refsynopsisdiv> + + <refsect1> + <title>Description</title> + + <para><command>nss-systemd</command> is a plug-in module for the GNU Name Service Switch (NSS) + functionality of the GNU C Library (<command>glibc</command>), providing UNIX user and group name + resolution for services implementing the <ulink url="https://systemd.io/USER_GROUP_API">User/Group Record + Lookup API via Varlink</ulink>, such as the system and service manager + <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry> (for its + <varname>DynamicUser=</varname> feature, see + <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry> for + details), + <citerefentry><refentrytitle>systemd-homed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, or <citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>.</para> + + <para>This module also ensures that the root and nobody users and groups (i.e. the users/groups with the UIDs/GIDs + 0 and 65534) remain resolvable at all times, even if they aren't listed in <filename>/etc/passwd</filename> or + <filename>/etc/group</filename>, or if these files are missing.</para> + + <para>This module preferably utilizes + <citerefentry><refentrytitle>systemd-userdbd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry> + for resolving users and groups, but also works without the service running.</para> + + <para>To activate the NSS module, add <literal>systemd</literal> to the lines starting with + <literal>passwd:</literal>, <literal>group:</literal>, <literal>shadow:</literal> and + <literal>gshadow:</literal> in <filename>/etc/nsswitch.conf</filename>.</para> + + <para>It is recommended to place <literal>systemd</literal> after the <literal>files</literal> or + <literal>compat</literal> entry of the <filename>/etc/nsswitch.conf</filename> lines so that + <filename>/etc/passwd</filename>, <filename>/etc/group</filename>, <filename>/etc/shadow</filename> and + <filename>/etc/gshadow</filename> based mappings take precedence.</para> + </refsect1> + + <refsect1> + <title>Static Drop-In JSON User/Group Records</title> + + <para>Besides user/group records acquired via the aforementioned Varlink IPC interfaces and the + synthesized root and nobody accounts, this module also makes user and group accounts available to the + system that are defined in static drop-in files in the <filename>/etc/userdb/</filename>, + <filename>/run/userdb/</filename>, <filename>/run/host/userdb/</filename> and + <filename>/usr/lib/userdb/</filename> directories.</para> + + <para>This is a simple mechanism to provide static user and group records via JSON drop-in files. Such + user records should be defined in the format described by the <ulink + url="https://systemd.io/USER_RECORD">JSON User Records</ulink> specification and be placed in one of the + aforementioned directories under a file name composed of the user name suffixed with + <filename>.user</filename>, with a world-readable access mode. A symlink named after the user record's + UID formatted in decimal and suffixed with <filename>.user</filename> pointing to the primary record file + should be created as well, in order to allow both lookups by username and by UID. Privileged user record + data (e.g. hashed UNIX passwords) may optionally be provided as well, in a pair of separate companion + files with the <filename>.user-privileged</filename> suffix. The data should be stored in a regular file + named after the user name, suffixed with <filename>.user-privileged</filename>, and a symlink pointing to + it, named after the used numeric UID formatted in decimal with the same suffix. These companion files + should not be readable to anyone but root. Example:</para> + + <programlisting>-rw-r--r--. 1 root root 723 May 10 foobar.user +-rw-------. 1 root root 123 May 10 foobar.user-privileged +lrwxrwxrwx. 1 root root 19 May 10 4711.user -> foobar.user +lrwxrwxrwx. 1 root root 19 May 10 4711.user-privileged -> foobar.user-privileged</programlisting> + + <para>Similarly, group records following the format described in <ulink + url="https://systemd.io/GROUP_RECORD">JSON Group Record</ulink> may be defined, using the file suffixes + <filename>.group</filename> and <filename>.group-privileged</filename>.</para> + + <para>The primary user/group record files (i.e. those with the <filename>.user</filename> and + <filename>.group</filename> suffixes) should not contain the <literal>privileged</literal> section as + described in the specifications. The privileged user/group record files (i.e. those with the + <filename>.user-privileged</filename> and <filename>.group-privileged</filename> suffixes) should + contain this section, exclusively.</para> + + <para>Note that static user/group records generally do not override conflicting records in + <filename>/etc/passwd</filename> or <filename>/etc/group</filename> or other account databases. In fact, + before dropping in these files a reasonable level of care should be taken to avoid user/group name and + UID/GID conflicts.</para> + </refsect1> + + <refsect1> + <title>Configuration in <filename>/etc/nsswitch.conf</filename></title> + + <para>Here is an example <filename>/etc/nsswitch.conf</filename> file that enables + <command>nss-systemd</command> correctly:</para> + + <!-- synchronize with other nss-* man pages and factory/etc/nsswitch.conf --> + <programlisting>passwd: compat <command>systemd</command> +group: compat [SUCCESS=merge] <command>systemd</command> +shadow: compat <command>systemd</command> +gshadow: files <command>systemd</command> + +hosts: mymachines resolve [!UNAVAIL=return] files myhostname dns +networks: files + +protocols: db files +services: db files +ethers: db files +rpc: db files + +netgroup: nis</programlisting> + + </refsect1> + + <refsect1> + <title>Example: Mappings provided by <filename>systemd-machined.service</filename></title> + + <para>The container <literal>rawhide</literal> is spawned using + <citerefentry><refentrytitle>systemd-nspawn</refentrytitle><manvolnum>1</manvolnum></citerefentry>: + </para> + + <programlisting># systemd-nspawn -M rawhide --boot --network-veth --private-users=pick +Spawning container rawhide on /var/lib/machines/rawhide. +Selected user namespace base 20119552 and range 65536. +... + +$ machinectl --max-addresses=3 +MACHINE CLASS SERVICE OS VERSION ADDRESSES +rawhide container systemd-nspawn fedora 30 169.254.40.164 fe80::94aa:3aff:fe7b:d4b9 + +$ getent passwd vu-rawhide-0 vu-rawhide-81 +vu-rawhide-0:*:20119552:65534:vu-rawhide-0:/:/usr/sbin/nologin +vu-rawhide-81:*:20119633:65534:vu-rawhide-81:/:/usr/sbin/nologin + +$ getent group vg-rawhide-0 vg-rawhide-81 +vg-rawhide-0:*:20119552: +vg-rawhide-81:*:20119633: + +$ ps -o user:15,pid,tty,command -e|grep '^vu-rawhide' +vu-rawhide-0 692 ? /usr/lib/systemd/systemd +vu-rawhide-0 731 ? /usr/lib/systemd/systemd-journald +vu-rawhide-192 734 ? /usr/lib/systemd/systemd-networkd +vu-rawhide-193 738 ? /usr/lib/systemd/systemd-resolved +vu-rawhide-0 742 ? /usr/lib/systemd/systemd-logind +vu-rawhide-81 744 ? /usr/bin/dbus-daemon --system --address=systemd: --nofork --nopidfile --systemd-activation --syslog-only +vu-rawhide-0 746 ? /usr/sbin/sshd -D ... +vu-rawhide-0 752 ? /usr/lib/systemd/systemd --user +vu-rawhide-0 753 ? (sd-pam) +vu-rawhide-0 1628 ? login -- zbyszek +vu-rawhide-1000 1630 ? /usr/lib/systemd/systemd --user +vu-rawhide-1000 1631 ? (sd-pam) +vu-rawhide-1000 1637 pts/8 -zsh +</programlisting> + </refsect1> + + <refsect1> + <title>See Also</title> + <para> + <citerefentry><refentrytitle>systemd</refentrytitle><manvolnum>1</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd.exec</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry><refentrytitle>nss-resolve</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + <citerefentry><refentrytitle>nss-myhostname</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + <citerefentry><refentrytitle>nss-mymachines</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd-userdbd.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd-homed.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + <citerefentry><refentrytitle>systemd-machined.service</refentrytitle><manvolnum>8</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>nsswitch.conf</refentrytitle><manvolnum>5</manvolnum></citerefentry>, + <citerefentry project='man-pages'><refentrytitle>getent</refentrytitle><manvolnum>1</manvolnum></citerefentry> + </para> + </refsect1> + +</refentry> |